The drilling of holes in concrete, as on construction sites, requires relatively large and heavy drills which are difficult to manipulate manually. Holes formed by the use of manually guided drills usually are not round and straight. Frequently drill bits are broken because their drive motors are not steady during the drilling operation.
To eliminate the above-mentioned undesirable effects and conditions, supporting structures have been devised to hold and guide the drill motor during the drilling process. These structures generally provide a base for mounting the drill, together with the motor powering the drill bit itself, to the surface in which a hole is to be drilled. Conventionally, a post is mounted on the base, the drill being guided toward and away from the surface along the post. The end of the post spaced from the base is steadied by a variety of devices, such as tie bars and support plates which are connected between the base and the post. A carriage is slidably secured to the post for mounting the drill, and it is known to drive the carriage mechanically along the post as by a rack and pinion mechanism.
In prior devices put into practice, the drill guide carriages are removable from the post only by removing the tie bars or support plates, e.g., from the end of the post farthest from the base, and by slipping the carriage over that end of the post. Because the carriage support structure had to be at least partially dismantled, removal of the drill-mounting carriage in prior coring and drill devices was cumbersome and time-consuming.
An adequately strong and rigid drill support base of the type of interest is a heavy structure in itself. Substantial weight is added to the support base by the carriage and the drill. The heavier the complete device, the more difficult it is to handle. When a hole is to be drilled on a vertical surface such as a wall, on an overhead surface such as a ceiling or in inaccessible places, the carriage and the drill usually have to be removed from the base to enable an operator to attach the base to such surface. After the base has been attached to the desired surface, the carriage, together with the drill mounted to it, must be slipped over the post of the prior art device. The tie bar must then be secured to the post before the drilling operation can commence.
Moreover, in practice, the carriages are frequently exchanged one for another in the substitution of one drill for another because each carriage is designed to mount a particular drill. Each time such a change is necessary, the apparatus must be dismantled and removed from the guide posts of prior devices, the carriage removed axially from the post, and a new one inserted.
Where a prior device is to be used high on a wall, the person attaching the carriage to the post has to reach back away from the wall (and away from a ladder or scaffold upon which the person may be standing) and guide the carriage and the drill motor onto the post. This procedure requires considerable physical effort and results in frequent accidents. These problems are especially acute where limited space is available and the operator has to work overhead.
An additional problem area is that of axial core drilling of concrete pilings and other manipulative operations at or near the end of a piling. Core drilling is used to extract a maximum amount of concrete from a piling prior to crushing the remaining concrete and severing the piling at a predetermined height. In the past, it has proven difficult to provide the core drill with the stability needed for drilling the concrete piling while still providing for a measure of apparatus portability and in-use flexibility.
The requirements of rigidity and non-yielding support for core drills has, in the past, resulted in the usage of large cumbersome devices for holding core drills. For example in U.S. Pat. Nos. 2,575,092 (Cole), 2,849,212 (Robbins), and 3,148,001 (Johnson), extensive anchoring to floor and ceiling or complicated linkage mechanisms are used to position, orient and impart drilling motion to the core drill or concrete saw apparatus. Similarly, in lighter less cumbersome devices, precision in locating the drill or saw is lacking since wear plates are necessary in the interfitting parts of the mechanism. Frequent maintenance is necessary particularly in the dust filled and gritty atmosphere in which such tools are used. The wear plates accumulate the abrasive dust and grind it into the mechanism. Examples of such devices are shown in U.S. Pat. No. 3,464,655 issued to A. Schuman.
These and other devices known to the prior art have a set overall size which is not readily dismantled for movement from job to job nor do they have the capability of readily positioning the core drill or saw in virtually any angular orientation.